1. Field of the Invention
This invention relates to a head positioning apparatus for tape recording heads and, more particularly, to a fine pitch lead screw and lever arm system for positioning a head in a tape cartridge back-up drive for data storage systems for personal computers.
2. Statement of the Problem
In tape cartridge back-up systems for personal computers, parallel tracks of data are recorded on a tape media in a data cartridge. A recording head with a single read/write gap must be positioned on the tracks such that the head gap centerline is within a prescribed dimensional tolerance of the recorded track centerline.
The problem of such track positioning has been addressed in other magnetic media devices which require a head to be positioned or repositioned to different tracks located on the media. For example, magnetic disk storage systems use stepper motors with lead screws to directly drive the head or use a band wrapped around a post in conjunction with a pivoting arm to position a head over the disk shaped media. Lever arms have been used to position the recording head.
In Thompson, "Fine Positioning Apparatus for Floppy Disk Drive", U.S. Pat. No. 4,630,145, two stepper motors are used to provide a coarse and a fine positioning to a read/write head. The first stepper motor engages a first lead screw which directly moves the head carriage to provide coarse adjustment. The second stepper motor is connected to a second lead screw which causes the first lead screw and the head carriage to move in fine adjustment.
In previous tape drives using tape cartridges, the head is positioned by directly driving the head with a lead screw and a follower nut on the lead screw. This method, although simple and straight forward, limits the resolution of the head positioning as a function of the pitch of the lead screw. Hence, a stepper motor is required having a very fine step increment for adequate positioning accuracy. In one commercial approach a spiral surface cam mounted to a stepper motor uses a lever arm actuated by the cam surface to position the recording head. While this approach uses the mechanical advantage of the lever arm, the cam is only able to rotate one full revolution. Hence, a very precise cam with a fine step increment on the stepper motor is required to obtain adequate accuracy in positioning of the head.
A need exists for a head positioning system which has combined the mechanical advantage of a fine pitched leadscrew/follower nut with a lever arm to maximize the resolution in positioning the recording head while at the same time minimizing the costs of the overall assembly.